480 FXUS66 KPQR 221820 AFDPQR Area Forecast Discussion National Weather Service Portland Oregon 1020 AM PST Sun Jan 22 2017 .SYNOPSIS...A rather deep low has developed along 130W and the associated front/deformation zone was lifting northeast out of southwest Washington and far northwest Oregon this morning. Some of the cool unstable air to the south of the low was spreading over the coastal waters and near the coast this morning and will slowly spread onshore through the afternoon and early evening. The main low offshore will drop south Monday for decreasing showers from south to north. As an upper ridge tries to expand onshore Monday night and Tuesday, a very weak upper disturbance will drop down from the north Tuesday for quite a bit of clouds and a few sprinkles. Another dying system is forecast to bring a small chance of precipitation to the area as it moves through the ridge Wednesday night and Thursday. Otherwise the weather will be much drier through the next week. && .SHORT TERM...Today through Tuesday...An impressive surface low in the mid 960s was along 130W north of the location of buoy 5 this morning. The associated front/deformation zone was lifting north of the area this morning with decreasing rain and mountain snow. Temperatures remain enough above freezing and the QPF expected the rest of the day is low enough so have dropped the winter weather advisories for the western and central Columbia River Gorge and the Upper Hood River Valley. However, there are a lot of cool unstable showers south of the low, some of which have been spreading into the coastal waters and near the coast already this morning with a few lightning strikes off Newport. These will spread onto the coast through the morning and afternoon, and may eventually spread farther inland this afternoon. With the low remaining offshore and with easterly surface pressure gradients over our area, the typical onshore flow that normally occurs is not really there, so the showers will tend move south to north parallel to the coast. However, they may still eventually spread slowly inland, then decrease in the early evening. The low will remain off the coast tonight but showers will be rather sparse due to the lack of onshore flow. The low moves south to off California Monday and Monday night with any remaining showers decreasing from north to south through the day and into the evening Monday. As an upper ridge over the northeast Pacific starts to expand into the Pacific Northwest Monday night and Tuesday, a very weak disturbance drops south into the forecast area that will produce rather cloudy conditions Tuesday across the area with a few sprinkles or mountain or Gorge flurries. Amounts will be very light. Tolleson .LONG TERM...No Changes. Previous discussion follows... Tuesday night through Saturday...Overall, dry as high pressure builds over the region. Will see seasonal temperatures for the region for rest of the week. One fly as appeared in the ointment...Wed night. Past and previous model runs have hinted at a front of varying strength moving into the region late Wed and Wed night. Am convinced now that will see some precipitation, albeit not much. Will put increased clouds for Wed and Thu, along with an increasing chance of rain late Wed afternoon and Wed night, then minor threat of showers on Thu. Rockey. && .AVIATION...Mostly VFR conditions across the region this morning under a broken to overcast mid cloud deck. A few pockets of MVFR cigs continue both with the main front (located along a roughly KAST-KHIO-KSLE line) as well as in some heavier showers behind the front. Will continue to see scattered showers through much of the day, and strongest of these may produce a thunderstorm, particularly near the coastal terminals, but confidence in development/timing sufficiently low to preclude mention in TAF for now. However, south wind gusts to 30 kt will continue along the coast through 02z. Elsewhere and otherwise, VFR through the period with only occasional MVFR cigs/vsbys in heavier showers. PDX AND APPROACHES...VFR conditions continue through the period with persistent cigs around 4000 ft. Occasional rain showers moving through the terminal area, with perhaps a brief MVFR period under heavier shower at some point this afternoon. Cullen && .MARINE...Gales continue over waters today as front continues to slide north across the region and deep surface low moves north along 130 W. Meanwhile, seas continue to slowly build again today, likely peaking in the 19 to 21 ft range later this evening. As the low pressure continues to push north today, then curls back and passes well south of the waters on Monday, expects winds shift from south today to east by late tonight and begin to ease as the surface pressure relaxes as the low moves away from the coastal waters. Seas will also slowly subside through the day on Monday, and lower below 10 feet by Monday night. Beyond Monday, marine conditions will remain rather quiet as high pressure builds over the NE Pacific and holds through much of the week, though a weak front may pass across the waters late Wednesday, and a larger west swell may arrive by late Wednesday night. Cullen && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Gale Warning until 10 PM PST this evening for Coastal Waters from Cape Shoalwater WA to Florence OR out 60 nm. Small Craft Advisory for Rough Columbia River Bar until 3 PM PST Monday. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.
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